1. Field
The present invention relates generally to communication, and more specifically to techniques for supporting handoff of a terminal between base stations of different protocol revisions in a code division multiple access (CDMA) communication system.
2. Background
Wireless communication systems are widely deployed to provide various types of communication such as voice, packet data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users, and may be based on code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), or some other multiple access techniques. CDMA systems may provide certain advantages over other types of system, including increased system capacity.
A CDMA system is typically designed to conform to one or more CDMA standards. Examples of such CDMA standards include “TIA/EIA/IS-95-A Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System” (hereinafter, the IS-95A standard), “TIA/EIA/IS-95-B Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System” (hereinafter, the IS-95B standard), and TIA/EIA/IS-2000 (hereinafter, the IS-2000 standard). Each CDMA standard may also be associated with multiple releases, each of which may include upgrades and new features for that standard. For example, the IS-2000 standard includes a Release 0, Release A, Release B, Release C, and so on. New CDMA standards and releases are continually proposed and adopted for use.
The IS-95A standard, which covers first generation CDMA, is designed mainly for voice communication. As such, it supports one call between a terminal and a base station at any given moment. The IS-95B standard, which covers next generation CDMA, supports voice and data communication (albeit at a relatively low data rate). The IS-2000 standard supports both voice and high-speed data communication. For the standard family comprised of IS-95 and IS-2000, each newer CDMA standard and release within that family incorporates the features and functionality defined in prior CDMA standards and releases, and further adds improvements and/or new features.
A CDMA standard/release may be assigned a specific signaling protocol revision level (P_REV) that may be used to unambiguously identify that standard/release. For example, on the base station side, IS-95B, IS-2000 Release 0, and IS-2000 Release A are associated with P_REVs of 5, 6, and 7, respectively. A new release of a given standard may thus be viewed as another standard. In general, a newer CDMA standard is backward compatible with older CDMA standards. A terminal or a base station designed to support a particular P_REV (e.g., P_REV=7) would then be able to support lower P_REVs (e.g., P_REVs=5 and 6) as well.
A wireless service provider may, due to different deployment options available, deploy different generations of base stations near or next to each other. This may result in compatibility issues if base stations with different P_REVs are used to support communication for a given terminal. For such a hybrid deployment, a terminal may be in communication with one base station of a particular P_REV and thereafter be handed off to another base station of a different P_REV. A higher P_REV is generally associated with more parameters since it supports more features and functions than a lower P_REV. Thus, if the terminal is handed off between base stations of different P_REVs, there are challenges associated with handling parameters that are defined in one P_REV and not in another P_REV.
There is therefore a need in the art for techniques to support handoff of a terminal between base stations of different protocol revisions that may be associated with different parameters used for communication.